"A methane gas explosion at the mine" was to blame, deputy of Tqibuli's city council, David Katamadze, said in televised remarks.
Georgia's Prime Minister Mamuka Bakhtadze offered condolences to the victims' families and declared today a day of mourning in the country of 3.8 million people.
"A decision has been taken to close the mine pending investigation" into the cause of the latest accident, he said in a statement.
Mining unions and labour rights groups have long complained about poor safety standards at Georgia's coal mines, where fatal accidents are common as many mines still use outdated Soviet-era equipment.
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